best use of an ice box

Submitted: Sunday, Apr 03, 2005 at 08:14
ThreadID: 21729 Views:5724 Replies:12 FollowUps:8
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Boat anchor or buy a fridge are not required answers, already had these.
As most of my trips are only 3 to 5 days a couple of time a year a fridge and second battery setup was is bit cost prohibutive.
The cooler Ive got is 85 ltrs, 5cm cold room isulation for walls,floor and lid, lid has a fridge type seal.
What Im looking for are peoples proven methods of getting effective chilling use out of an ice box for 3 to 4 days.
Type of ice ,location in box ie high or at bottom.
Is it better to drain the melt water or leave it in etc
Use of a cheaper "esky" for high use items like drinks, butter and milk etc.
Over to the more informed than I.
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Reply By: Member - toohey - Sunday, Apr 03, 2005 at 08:36

Sunday, Apr 03, 2005 at 08:36
giday guzzi
i get the best results from my evercool esky using block ice not crushed or i freeze 3 two litre juice cont.before leaveing home these can last 3 days,i don't drain the water hope this helps.
regards toohey
AnswerID: 104870

Reply By: Member - Jimbo (VIC) - Sunday, Apr 03, 2005 at 08:42

Sunday, Apr 03, 2005 at 08:42
Guzzi,

Block Ice, the bigger the blocks the longer they last and drain the water.

I used to get up to 3 days out of a block (bought from a shop) in a Coleman esky (cheapie) in temps of around 25C. Making your own blocks at least a week in advance to get them REALLY frozen also helps.

Cheers,

Jim.
AnswerID: 104871

Reply By: Member - Banjo (SA) - Sunday, Apr 03, 2005 at 08:54

Sunday, Apr 03, 2005 at 08:54
Yep - been there - big blocks are the go - not always available - usually have to go to the actual iceworks in the towns you visit (but many have now gone) to access the blocks..... and the purists would say that IF you have the room for the water, it should stay (until a problem), seeing its colder than the air outside......slows the block melt if it stays.
AnswerID: 104875

Reply By: Member - Jimbo (VIC) - Sunday, Apr 03, 2005 at 09:04

Sunday, Apr 03, 2005 at 09:04
I disagree with the leave the water in theory.

Water is ice in its defrosted state and by leaving it there you are asking the ice to keep the water cold. Much in the same way your freezer at home works more efficiently when it is not iced up ie it works best when the cooling element cools the air around the food rather than keeping the ice buid up frozen which in turn keeps the food frozen (albeit not as cold), and has to work harder.

Keeping food cold by putting it in water that is relying on the ice to keep it cold makes no sense IMHO, but I will defer to anyone who can provide scientific evidence otherwise. Bloody messy as well, a few drops of milk or meat juices will turn the water into a cess pit that may cross contaminate your other food.

Cheers,

Jim.
AnswerID: 104876

Follow Up By: shaggy - Monday, Apr 04, 2005 at 12:38

Monday, Apr 04, 2005 at 12:38
Jimbo,
you have a few misconceptions. When ice and water are present together, they are both at 0 deg C. This is called an invariant triple point. The ice is not being "asked to keep the water cold". They are both at same temperature. Your ice will last longer if kept in already cold water. Do not drain water, and you are providing the ice with a liquid which is at 0 deg C and has a lot of thermal mass. Water has the highest specific heat capacity of all liquids, meaning it takes the most energy for it to change temperature. 4.18 J/g/deg C
If you drain the water, your ice is now a smaller mass then when you have water and ice, and will not last as long. It cannot due to fundamental physics and thermodynamics. The larger something is, the more energy is required to change its temperature.
Your cup of tea will cool off much quicker then your bath tub full of boiling water. Same goes with ice. A frozen cup of water will melt a lot quicker then a frozen bathtub full.
Regarding refrigerator efficiencies, that is not a good analogy for various reasons which I do not have the time to go into here...

cheers
Shaggy
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FollowupID: 362246

Follow Up By: Member - Jimbo (VIC) - Monday, Apr 04, 2005 at 19:49

Monday, Apr 04, 2005 at 19:49
Shaggs,

Of course the ice is abeing asked to keep the water cold. I they were both at the same temp as each other they would be in the same state ie either solid or fluid.

Ice is below 0C. It is actually at -18C if it is in a freezer at that temp. Try this: stick a probe thermometer in water and freeze it at -18C. You will find the temp at the core of the ice is the same as its surroundings.

The other point you have missed is that keeping fluid cold takes more energy than keeping air cold. Why do you think that it is that air blowing over a cooling coil at say 20C (such as in an air condtioner) will hit an immediate temp of say 4C, when pouring water over that same coil has a minimal change to its temp? Why? Air is less dense than water therefore it is more susceptible to change.

Try this. Put two identically sized ice cubes in two glasses. Add very cold water (say 0C or close to it) to one glass and cover with cling wrap. Do the same to another glass with ice cubes on their own and see which ice cubes melt first.

Interesting conversation mate.

Cheers,

Jim.
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FollowupID: 362291

Follow Up By: Wok - Monday, Apr 04, 2005 at 23:45

Monday, Apr 04, 2005 at 23:45
Jim & Shaggy,

Shaggy is correct in the Physics & Jim is correct in practice.

If you take into account the difference in surface areas of the two scenes it is clear why water should be removed....water in a cooler provides a large surface area ie the thermal gain is higher[water been a better conductor then air]

With current iceboxes being rectangular, the thermal gain >>>>>advantage of themal mass.

Have an apple each :)

Cheers
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FollowupID: 362320

Follow Up By: Member - Jimbo (VIC) - Tuesday, Apr 05, 2005 at 07:23

Tuesday, Apr 05, 2005 at 07:23
Just to satisfy my own theory lasyt night I stuck a probe thermometer in a cup of water in the freezer. This morning I checked and the internal temp is -19C. Therefore the internal temp of the ice will remain at that and the suface area will be at 0 (the temperature of melting ice).

Cheers,

Jim.
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FollowupID: 362327

Follow Up By: shaggy - Tuesday, Apr 05, 2005 at 18:26

Tuesday, Apr 05, 2005 at 18:26
SHOULD YOU DRAIN THE WATER FROM A COOLER OR LEAVE IT IN ?

As in many of life's conundrums, all we can say is, "it depends".
Nonetheless, I will attempt a response and tell you what assumptions I made to eliminate variables and get to an answer (i.e., I couldn't solve
your problem so I made one up that I could. I'll argue that, in this
case, describing the thought process is more important than the actual result).

First off, I'm going to assume that the contents of the chest are
waterproof, so we're interested in draining the chest only to better
keep the contents cold, not to keep the egg salad sandwiches dry.

Second, I'm going to assume that the chest is reasonably well insulated,
so that rate of heat transmission through the chest walls is small
compared to the rate of heat transmission from the inner chest wall to
the contents, be it through air or water. This permits me not to
worry about the insulating properties of air inside the chest versus
water.

Third, I'm going to assume that both ice and food have been added
a long time ago, and thermal equilibrium has been reached. That means all ice, water, and food inside the chest are at 0 deg C.
Therefore, we don't generally have to worry about hot spots or cold
spots, or significant convection within the chest.

Fourth, to keep my mental model simpler, I'm going to assume that the
chest has been placed in an open area exposed to free ambient air, and
protected from the sun. For example, it's sitting in the shade of a
tree. Also, let's assume that we're dealing with ordinary summer day temperatures, not the surface of Mercury. This allows a simple model of heat transfer to apply.

Let's consider what happens when there's lots of ice in the cooler.
The temperature will remain 0 deg C, regardless of how much water
is there; draining water won't make things colder. Will draining water
cause the ice to melt slower or faster? Neither -- the rate of heat
transfer into the chest depends on the temperature difference between
the interior and exterior of the chest, i.e., the ambient air temperature.

Every Joule of heat entering the chest is offset by the melting of a
smidgeon of ice (and if I had a Calc handy, I'd tell you exactly how much; this is the so-called heat of crystallization.)
Melting ice remains at exactly its melting point until it's all melted,
as do all (?) other materials that undergo a well-defined phase change
(conversion from solid to liquid).

So it's only this temperature difference, and not the amount of water in
the chest, that matters. So I claim, under the assumptions given, that
from a "conservation of ice" standpoint it doesn't matter if you
drain the chest while the ice is melting.

Now let's consider what happens when it's time to add ice.
Of course, you will need to drain the chest eventually
to make room for more ice, but that's another matter entirely.

There are two conditions to consider: the first is that the ice
you are going to add has reached 0 deg C and is already melting (say,
you had brought along extra to replenish the cooler). Under this
condition, it doesn't matter if you drain the water upon adding more
ice. The water won't melt the ice faster (the water is already at 0 deg C)

The second condition is that you are going to add ice directly out of a
freezer. This ice will be much colder than 0 deg C, and it will not
have begun melting. In this case, it's slightly advantageous to have
water in the chest. Upon adding this very cold ice to the chest, it will
warm up to 0 deg, reach equilibrium, and we have the case previously
consider. So we need to consider how this fresh ice reaches equilibrium in the way that best conserves the "extra joules of cold" in the ice because it's below its melting point.

If liquid water is present when this very cold deep freezer ice is added,
a small portion will freeze as it gives up heat to warm the ice to its melting point. Heat transfer into the chest will remain approximately constant, assuming that there's sufficient water to allow the ice to
warm and the water to freeze quickly so that 0 deg C equilibrium is
reached quickly. This effectively stores the excess cold as a bit of
additional ice. This is because the heat necessary to warm the deep
freezer ice up to the melting point comes from heat in the liquid water,
a bit of which freezes. (I'm assuming a couple of things here:
first, that the rate of this heat transfer far exceeds heat transfer
through the chest walls, so this effect dominates any increased
heat transfer due to colder contents. Second, I'm assuming that we're
adding about as much, or less ice than we started with; if you add *lots* of deep freezer ice there's potential to freeze all the water, but I
think this to be unlikely in practice. If it should happen, then my
argument below applies).

If water is not present, the food will try to cool below 0 deg C as it
gives up heat; if there's enough free water in the food a little
will freeze and the food temp will hold at 0 deg C as the ice warms and
eventually begins to melt. This is the same situation as if we hadn't
drained the chest.

If the moisture in the food is actually a solution (e.g., due to dissolved
salt or sugar), the freezing point will be somewhat lower and the ice will warm only to this temperature below 0 deg C. Once all moisture is frozen, then the food will cool below the freezing point until equilibrium with the ice is achieved at some temperature below 0 deg C. In these instances I think we will wind up melting the ice sooner than if there were water in the cooler.

This can be seen by considering what happens to the extra
joules of "cold" (that is, the heat it takes to warm deep freezer ice
up to the melting point). I've explained before how freezing the
liquid inside the chest quickly captures and "stores" the "excess cold".

If there is no free water in the chest and the contents chill below 0 deg
C (for reasons described above), then the remaining warming of the
deep freezer ice up to melting point must occur due to heat transfer
through the chest. If the rate of heat transfer were constant, then these
"additional joules of cold" would be lost at the same rate as if they first
froze the water inside the chest, and the total amount of time needed to
melt all of this ice would be the same as the case where the deep freezer ice is added to an undrained chest. But the heat transfer rate will increase because the contents have reached a colder equilibrium
temperature; therefore these extra joules will be lost more quickly.
This means the total time needed for melt the ice (i.e., the time needed
to transfer enough joules through the chest walls) may be a bit shorter.

My judgment is that difference will be small but not negligible. The heat
required to melt an ice cube at its melting point is very much larger
than the heat required to raise that cube's temperature 1 deg when it
more than 1 deg below freezing, or fully melted, for that matter.
(I think the factor is about 150 -- that is, it takes as much heat to melt
one ice cube once it's temperature is at equilibrium
it does to raising the temperature of the resulting liquid to 82 deg C.
That's why ice cubes are so effective at cooling! Conversely, it takes as
much cooling to freeze an ice cube from water at the freezing point as it
does to chill the resulting cube to -83 deg C. In other words,
there's some, but not a huge amount of "excess cold" stored in deep
freezer ice -- perhaps an additional 20% joules of heat are absorbed for
ice at -18 deg C versus ice already at the melting point. On the other
hand, this implies that, properly conserved, this "excess cold" could
be used to chill the chest contents 20% longer.

Thus, this argues that one shouldn't drain *all* the water out of a chest
when replenishing the ice. But this may happen naturally, for there will
always be residual water, plus foodstuffs kept in a cooler tend to
have significant moisture content (who keeps potato chips in a cooler?)

Having water in the chest
minimizes the amount of warm air that can enter the chest when ice is
added; draining water out of the chest will cause warm air to be sucked
in.

Finally, let's consider what happens once the ice has all melted and
there's no more available to replenish the chest. The temperature
inside the chest will begin to rise. The heat transfer in the chest
continues to be proportional to the temperature difference between
inside and outside. For every unit of heat transferred in, the
temperature rise in the chest will be inversely proportional to the
thermal capacity ("thermal mass") of the chest contents. Keeping
the chest full of water will be advantageous, for there's simply more
mass that has to be warmed up. (Proof: consider inverse problem --
if you are going to cool off the chest from ambient temperature, common sense would say to remove all extraneous water and put the food in direct communication with the ice; no need to cool off the water remaining from the last batch of melted ice).

So bottom line, from a "conservation of ice" point of view, under
the assumptions given, there is no difference on whether you drain the
cooler while the ice is melting, there is a some potential benefit to
keeping the water in when replenishing with freezer-fresh ice, and there is definite benefit for keeping water in once the ice is melted and you are trying to keep things as cold as possible as long as possible.

Hope this clears everything up

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FollowupID: 362413

Follow Up By: Wok - Tuesday, Apr 05, 2005 at 23:27

Tuesday, Apr 05, 2005 at 23:27
Shaggy,

IMHO the difference in thermal conductivity between water & air is not a trivial variable[assumption #2]. If one factored this in, would one not expect that the Joule of heat that entered the system would reach the ice faster? [ignoring radiation & convection paths]

IOW the slope of the gradients is different [start temp & end temps are the same]

Test your model with 2 compunds, [1] a perfect insulating liquid state & [2] a perfect conducting liquid state. The model doesn't fit.
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FollowupID: 362466

Reply By: Dodgy - Sunday, Apr 03, 2005 at 09:05

Sunday, Apr 03, 2005 at 09:05
Gidday Guzzi,
Dry ice is also a good one.. I've kept it for almost 10 days on fraser island. I only put hard frozen stuff in the esky and only went into it once a day. The secret is to stay out of it and keep it covered.. Your dry ice will be wrapped in paper.. put extra sheets of paper around it and put a small tear in it.. Place it towards the top of the esky and in the middle and pack party ice around it and across the top of the frozen goods to form a blanket. i then put a thick towel over the lot to act like a insulating blanket. i take the frozen stuff out once a day and put it into another esky to thaw and to keep chilled stuff cool.. I hope this helps a little.
Regards Dodgy..
Keep your whistle wet and your powder dry.. ;-)
AnswerID: 104877

Reply By: Shaker - Sunday, Apr 03, 2005 at 09:22

Sunday, Apr 03, 2005 at 09:22
We freeze a 'kitty litter' tray full of water & put in the bottom of our EvaKool icebox, which we use to supplement the Engel.
Then we use home made 'solid' ice cubes, not the hollow 'party ice' that are designed to melt quickly in drinks.
We find that this combination along with pre-chilled food or drinks, lasts for between 8 & 12 days, depending on usage & conditions.
AnswerID: 104880

Reply By: Big Woody - Sunday, Apr 03, 2005 at 10:01

Sunday, Apr 03, 2005 at 10:01
Hi Guzzi,

We have gone sailing in the Whitsunday's for 3 weeks of every January for the last 15 years. We have only ever used ice-boxes (3 of them) and at the end of the 3 weeks, we have had to defrost a can of drink before you can drink it.

The first secret is good quality ice boxes, I have used the fridge panel ones before, I think they are pretty good but not quite as good as some of the commercially available ice-boxes but they will cost as much as a freezer anyway.

The second secret is that everything that goes into the ice box is deep frozen for at least a month before we go away in big chest freezers cranked as low as they will go.
Pack the ice box so that there is very little air space.
By good quality Block ice and freeze it further at home for a month before you go away too.
Drain the water every day.
Buy crushed ice to fill in all of the gaps around your food.
Once a week we would drop in at Hamilton Island and purchase fresh ice to pack around the loose items of food.
Know how you pack the ice-box and where everything is so that the lid is only open for a few seconds each time you open it and limit the number of times it is opened in the middle of the day.
Keep the ice boxes out of the sun at all times and cover them with thick blankets. We just have a thick old sleeping bag over each one which makes them quite comfy to use as seats to sit at the table for meals.

The reason we used ice boxes is that it is not really safe to run any LPG appliance inside a yacht and at the time, solar set-ups were way too expensive.

My friend here in Bundaberg owns a refrigeration business and has been telling me all of the benefits of Dry ice. He has now started producing it to sell and I am quite impressed. Considering how long it lasts as well as not having any problems associated with the melting of normal ice, I would consider it to be the best option and quite cost effective when you are going away for extended periods.

I hope this helps you figure out what set-up is going to suit you the best.

Regards,
Brett
AnswerID: 104897

Reply By: Nudenut - Sunday, Apr 03, 2005 at 10:05

Sunday, Apr 03, 2005 at 10:05
Block ice from ice facory is only about -12 to -15 (or even warmer in some cases)
make your own if you have a freezer..this should bring it down to -20 to -23 or a little colder. (I have noticed cans of nectar frozen when i arrived at destination)

Water left in esky only increases thermal gain to ice causing it to melt quicker.

Leave ice at bottom.

Dry ice can cause things to freeze as it is a very cold product "in itself" and is costly

AnswerID: 104899

Reply By: Member - Karl - Sunday, Apr 03, 2005 at 11:50

Sunday, Apr 03, 2005 at 11:50
My 10c worth. I use a 100L ice box, as I can't afford the prices they are asking for the car fridges, and I start to cool it down three days before use by putting ice into it.

When I go to pack it for the trip I remove the water, pack it and fill it full of ice. I start to freeze all of the frozen food at least two - three weeks before I pack it to make sure that it's frozen (therefor takes longer to thaw).

If using ice from the Servos etc - I find that by opening the bags the ice will keep things colder but melts quicker than if it's keep in the bag - so I do a mixture of each.

If making your own ice, try using old two litre cordial bottles - that way you will have cold drinking water and your not throwing away vauble water.

Hope this helps.
AnswerID: 104909

Reply By: Derek - Sunday, Apr 03, 2005 at 20:58

Sunday, Apr 03, 2005 at 20:58
Guzzi
My science class at uni has just had to do the excercise as an assignment. Every group found that dry ice lasts the longest, works best if wrapped in paper and if ice melt is drained off regularly.
AnswerID: 104980

Follow Up By: Member - Jimbo (VIC) - Sunday, Apr 03, 2005 at 21:07

Sunday, Apr 03, 2005 at 21:07
Dry ice melts and turns into water?

Dry ice is frozen, liquified, carbon dioxide which is at about -80C. As it melts is vapourises into carbon dioxide gas.

Not sure what you mean Derek, are you talking about using the dry ice to keep the ice frozen?

Cheers,

Jim
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FollowupID: 362191

Reply By: flappa - Monday, Apr 04, 2005 at 09:07

Monday, Apr 04, 2005 at 09:07
Like others , we make our own ice.

Block ice made from half icecream containers , and frozen Cordial or Milk bottles.

We drain the water away
AnswerID: 105039

Reply By: guzzi - Monday, Apr 04, 2005 at 21:35

Monday, Apr 04, 2005 at 21:35
To all that replied many thanks.
Lots of good ideas.
as he wanders away contemplateing carbon dioxide gas, melt water and where to put the beer................
AnswerID: 105194

Follow Up By: Mainey (WA) - Thursday, Apr 07, 2005 at 12:31

Thursday, Apr 07, 2005 at 12:31
One thing to remember, as stated above, is the water at the bottom of the cabinet would be contaminated with... bacteria.

If bad bacteria, (salmonella etc) comes into contact with food, as it will in contaminated water, you then to some degree risk life....

Reading this post confirms why I have ordered a new fridge, lol.
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FollowupID: 362648

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